Strange (Re)Drawing in Image, anyone any idea ?

Hi,

I seem to have messed up my image (based on the CI built Seaside 3 Pharo 1.2 image), the result is strange (re)draw patterns, drawing outside windows, strange text rendering, artifacts, etc. This is an example screenshort:




I tried several things, but the problem remains, I am inclined to think it is image related. Has anyone every seen something similar ? Any idea how I could try to fix it ?

TIA,

Sven